It has been known that NGF acts as a survival and maintenance as well as neurite outgrowth factor for sympathetic neurons and sensory neurons in the peripheral nervous system [Physiol. Rev., vol. 60, pages 1284-1335 (1980) and Ann. Rev. Biochem., vol. 51, pages 845-868 (1982)] and that high NGF levels were found in the regions innervated by the magnocellular neurons (hippocampus, neocortex, olfactory bulb), and in the regions containing the cell bodies of these neurons (septum, nucleus of the diagonal band of Broca, nucleus basalise of Meynert) and that NGF acts as neurotrophic factor for magnocellular cholinergic neurons [EMBO J., vol. 4, pages 1389-1393 (1985)].
NGF has also been drawing attention in terms of relation to central nervous diseases such as senile dementia of Alzheimer type [Science, vol. 232, page 1341 (1986)], Huntington's chorea [Neurosci. Lett., vol. 40, No. 2, pages 161-164 (1992)], and to peripheral nervous diseases such as various neuropathies {diabetic neuropathy [Brain Res., vol. 634, pages 7-12 (1994)], neuropathy caused by drugs [Brain Res., vol. 640, pages 195-204 (1994)] and the like}, Riley-Day syndrome [Japanese J. of Clinical Medicine, vol. 50, No. 4, pages 178-183 (1992)], traumatic neuropathy [Pharmacol. Ther., vol. 65, No. 1, pages 1-16 (1995)], amyotrophic lateral sclerosis (ALS) [Nature Medicine, vol. 1, No. 2, pages 168-172 (1995) and the like.
An attempt has been made to use NGF or a NGF-like substance for the treatment of central and peripheral nervous diseases described above [Brain and Nerve, vol. 43, No. 12, pages 1101-1112 (1991) and the like]. However, these substances are all proteins, and when they are used as drugs, their stability, antigenicity and the like will become a problem. Therefore, a compound useful as a drug for potentiating the NGF activity has been desired.